The present invention relates to error correction feed back controls with a reverse interpolation of an identifiable correction to a plurality of proximate grid points based on a selectable time interval for correction as well as a number of iterations to be completed in the interval.
In many systems, such as an automobile engine fuel control system, the air/fuel ratio may be adjusted by a proportional-integral control loop that provides a fuel multiplier control signal to the engine. A combustion mixture or air/fuel ratio detector on the engine provides a signal to the control loop identifying whether the combustion has been completed as desired. The difference between the air/fuel ratio as designated and the effective combustion create an error signal introduced to the proportional-integral control loop. While such a system provides continuous adjustment, the loop does not provide a means to conform the correction to a desired objective, such as efficiency or power, under a wide variety of operating conditions that may be encountered by the engine, including the demand for power and the speed at which the engine is traveling.
Certain systems have been known to incorporate reverse interpolation algorithms for training a lookup table. While reverse interpolation changes a plurality of points in response to changes detected at a read point, such training may continue over prolonged periods or indefinitely without obtaining sufficient degrees of accuracy for a desired goal.
The present invention overcomes the above mentioned disadvantages by providing a method of reverse interpolation for training a 3D lookup table within a selected fixed time interval, and adjusting the difference between the desired goal and a current response at a plurality of grid points in relation to the slope with respect to a given read point. In the preferred embodiment, a normalized throttle position signal and a normalized speed signal are input along with an error signal to an adaptive algorithm performing the 3D reverse interpolation. As a result, the present invention provides an adjusted output for a lookup table that is trained within a limited period of time and with well calculated steps of adjustment that establishes substantially complete adjustment over the limited time.